io_uring: refactor io_alloc_req

Replace the main if of io_flush_cached_reqs() with inverted condition +
goto, so all the cases are handled in the same way. And also extract
io_preinit_req() to make it cleaner and easier to refer to.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/1abcba1f7b55dc53bf1dbe95036e345ffb1d5b01.1628471125.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 620ab4c..8892747 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1702,6 +1702,19 @@ static void io_req_complete_failed(struct io_kiocb *req, long res)
        io_req_complete_post(req, res, 0);
 }
 
+/*
+ * Don't initialise the fields below on every allocation, but do that in
+ * advance and keep them valid across allocations.
+ */
+static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
+{
+       req->ctx = ctx;
+       req->link = NULL;
+       req->async_data = NULL;
+       /* not necessary, but safer to zero */
+       req->result = 0;
+}
+
 static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
                                        struct io_comp_state *cs)
 {
@@ -1744,45 +1757,31 @@ static bool io_flush_cached_reqs(struct io_ring_ctx *ctx)
 static struct io_kiocb *io_alloc_req(struct io_ring_ctx *ctx)
 {
        struct io_submit_state *state = &ctx->submit_state;
+       gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
+       int ret, i;
 
        BUILD_BUG_ON(ARRAY_SIZE(state->reqs) < IO_REQ_ALLOC_BATCH);
 
-       if (!state->free_reqs) {
-               gfp_t gfp = GFP_KERNEL | __GFP_NOWARN;
-               int ret, i;
-
-               if (io_flush_cached_reqs(ctx))
-                       goto got_req;
-
-               ret = kmem_cache_alloc_bulk(req_cachep, gfp, IO_REQ_ALLOC_BATCH,
-                                           state->reqs);
-
-               /*
-                * Bulk alloc is all-or-nothing. If we fail to get a batch,
-                * retry single alloc to be on the safe side.
-                */
-               if (unlikely(ret <= 0)) {
-                       state->reqs[0] = kmem_cache_alloc(req_cachep, gfp);
-                       if (!state->reqs[0])
-                               return NULL;
-                       ret = 1;
-               }
+       if (likely(state->free_reqs || io_flush_cached_reqs(ctx)))
+               goto got_req;
 
-               /*
-                * Don't initialise the fields below on every allocation, but
-                * do that in advance and keep valid on free.
-                */
-               for (i = 0; i < ret; i++) {
-                       struct io_kiocb *req = state->reqs[i];
+       ret = kmem_cache_alloc_bulk(req_cachep, gfp, IO_REQ_ALLOC_BATCH,
+                                   state->reqs);
 
-                       req->ctx = ctx;
-                       req->link = NULL;
-                       req->async_data = NULL;
-                       /* not necessary, but safer to zero */
-                       req->result = 0;
-               }
-               state->free_reqs = ret;
+       /*
+        * Bulk alloc is all-or-nothing. If we fail to get a batch,
+        * retry single alloc to be on the safe side.
+        */
+       if (unlikely(ret <= 0)) {
+               state->reqs[0] = kmem_cache_alloc(req_cachep, gfp);
+               if (!state->reqs[0])
+                       return NULL;
+               ret = 1;
        }
+
+       for (i = 0; i < ret; i++)
+               io_preinit_req(state->reqs[i], ctx);
+       state->free_reqs = ret;
 got_req:
        state->free_reqs--;
        return state->reqs[state->free_reqs];
@@ -6569,6 +6568,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
        unsigned int sqe_flags;
        int personality, ret = 0;
 
+       /* req is partially pre-initialised, see io_preinit_req() */
        req->opcode = READ_ONCE(sqe->opcode);
        /* same numerical values with corresponding REQ_F_*, safe to copy */
        req->flags = sqe_flags = READ_ONCE(sqe->flags);